JP 2009-530526T (Reference 1) discloses a vehicle hydraulic circuit with a motor including a hydraulic piston including at least two cylinder chambers (advancing chamber and retarding chamber) that act in mutually opposite directions, configured such that an external force acts alternately or in one direction in the cylinder chamber, the hydraulic piston is moved by a differential pressure between the cylinder chambers, and the differential pressure is generated from a hydraulic source, such as a hydraulic pump. The hydraulic circuit is used for a cam shaft timing adjuster (valve timing controller) and uses a hydraulic load by a force that acts on a negative side caused by opening at least one check valve among the alternating external forces in addition to the hydraulic load by a changeover device for the movement of the hydraulic piston.
In the valve timing controller described in Reference 1, the check valves are provided in return passages of hydraulic oil from cylinder chambers that act in mutually opposite directions, and a downstream side of the check valve is connected to a pressure supply pipe for supplying the hydraulic oil to the cylinder chamber. The valve timing controller realizes the circulation of the hydraulic oil from one cylinder chamber to the other cylinder chamber by providing the check valve, and it is possible to quickly move the hydraulic oil to the cylinder chamber.
JP 2017-048793A (Reference 2) describes a variable camshaft timing device (valve timing controller) can operate with the pressure generated by camshaft torque energy for transmitting a fluid from one working chamber to the other working chamber, can operate through a pressure source of an external fluid so as to discharge the contents in opposing working chambers at the same time when filling one working chamber, and can operate using both modes simultaneously.
In the valve timing controller described in Reference 2, the control valve is a spool valve having a spool, the spool has a cylindrical land that is slidably accommodated in a sleeve inside a bore of a center bolt, and the sleeve has a recess portion that connects the plurality of ports to each other. The spool of the valve timing controller is configured to have a central passage, and to be divided into a working central passage and an inlet central passage by a recirculating check valve and an inlet check valve provided in the central passage. The valve timing controller can reduce the package size of the valve timing controller by providing the recirculating check valve in the central passage.
In the valve timing controller described in Reference 1, since corresponding check valves are respectively required for each cylinder chamber (advancing chamber and retarding chamber) that act in mutually opposite directions, there is a problem because the structure becomes complicated. In the valve timing controller described in Reference 2, since the check valve (recirculating check valve and inlet check valve) is disposed inside the spool, the structure becomes complicated. In addition, since the check valve is disposed in a narrow space inside the spool, due to the restriction of the space, it is inconvenient that the size or the shape of the check valve is restricted.
Thus, a need exists for a valve timing controller which is not susceptible to the drawback mentioned above.